Yonsei Advanced Science Institute

The electrogenerated chemiluminescence (ECL) behavior of luminol on a glassy carbon (GC) electrode modified with gold nanocluster-graphene-Nafion composite films has been investigated in neutral aqueous solution (pH 7). In the present study, atomically well-defined gold nanoclusters of Au25(SC6H13)18, where SC6H13 is hexanethiolate, were used for the preparation of composite films. Due to the highly enhanced electrocatalytic activity of the composite towards the reduction of molecular oxygen, strong cathodic luminol ECL response related to the electrochemical oxygen reduction was observed on the composite-modified GC electrode at ca. – 1.34 V vs. Ag/AgCl (3 M NaCl) in a neutral aqueous solution, while no cathodic ECL response was observed on a bare GC electrode. The addition of hydrogen peroxide led to a decrease in the cathodic luminol ECL response related to the oxygen reduction, whereas a new ECL response related to the electrochemical reduction of hydrogen peroxide was observed at ca. – 0.01 V vs. Ag/AgCl (3 M NaCl). The possible ECL mechanisms were discussed. Under the optimum conditions, the ECL response was linear with the concentration of hydrogen peroxide in the range of 1.0 × 10−8 M ~ 4.0 × 10−6 M with a detection limit of 2.21 × 10−9 M (S/N = 3) in neutral aqueous solution.